A typical design for lifting trucks includes load forks connected to a telescoping mast with two or more stages. In this configuration, the lifting truck can maximize potential lifting height while maintaining a low center of gravity during transport. This also allows the truck to pass through openings with much lower clearance than the potential lifting height of the truck. For most lifting trucks with telescoping masts, the load forks have a limited vertical range without the use of the telescoping mast. This is called free lift. However, when lifting to greater heights, where one or more stages of the telescoping mast are raised, the effective load lifted by the truck is increased by the weight of the moving stages.
Each stage is constructed with three vertical beams arranged so that the footprint of the beams forms an isosceles triangle. The stages are coupled in known manner so that all stages move in relation to each other during a lift. The guides and lifting means are arranged close to the vertical beams on the sides of the mast and the truck. The third vertical beam increases the strength and rigidity of the mast against both transverse and longitudinal forces.
One of the shortcomings of this design is that added force is required to lift the load when the telescoping feature of the mast is utilized. In addition to the load forks and the telescoping mast, many trucks also lift the operator, the operator's platform, and/or other means for load handling such as a fork pivot means. These extra weights represent an inefficient use of energy that has not been solved by current designs.